Water bed mattress



FIG. 1 is a front, top and left side perspective view of a waterbed mattress showing my new design;

FIG. 2 is a side elevational view;

FIG. 3 is a front elevational view;

FIG. 4 is a bottom perspective view.

The broken lines inside the accented corners indicate slight changes in contour and the randomly placed non-parallel lines on the rest of the mattress are meant to show that the mattress is baggy. 

The ornamental design for waterbed mattress, substantially as shown and described. 